Power converting devices including a switch such as a contactor that is connected to an output of a DC power supply have been known (for example, JP 2006-42459 A).
A system 1000A in which such a power converting device 100A is used includes the power converting device 100A, a DC power supply (battery) 3, a vehicle control unit 5, a DC power supply from the DC power supply 3, a driving motor 4, and wheels 6.
The power converting device 100A includes, in an inverter housing, a pulse width modulation (PWM) power conversion module 13 configured to control the power from the DC power supply 3 using the vehicle control unit 5 and a power conversion control unit 12, and to convert the power from DC power to AC power, a discharge control circuit 11, an interlock circuit 21, a photocoupler 22 connected to the interlock circuit 21, and a switch 24 controlled by the vehicle control unit 5. A smoothing capacitor 23, which is an electrolytic capacitor, and a first discharge resistance 25 are connected in parallel to each other between a high potential input terminal and a low potential input terminal of the power converting device 100A. The first discharge resistance 25 discharges the electric charge of the smoothing capacitor 23 when the discharge control circuit 11 stops functioning.
The DC power from the DC power supply 3 is converted to AC power at the pulse width modulation (PWM) power conversion module 13 to drive the driving motor 4 and rotate the wheels 6. While the driving motor 4 is not being driven (during regeneration), three-phase AC power generated by the driving motor 4 is converted to DC power, which is supplied to the DC power supply 3.
In the power converting device 100A, the DC voltage outputted from the DC power supply (battery) 3 to the internal circuit (discharge control circuit 11, PWM power conversion module 13) is controlled by turning on/off of the switch 24 (FIG. 2).
The conventional power converting device 100A detects the fusing of the contacts of the switch 24 while the DC power supply 3 is outputting the DC voltage. Thus, the fusing of the switch 24 is detected while the output of the DC power supply 3 and the internal circuit are electrically connected to each other.
Therefore, if the switch 24 is fused (melted) in the conventional power converting device 100A, an unintended DC voltage may be outputted to the internal circuit due to the ON-state failure caused by the melting of the switch 24.